The study will evaluate risk factors for subarachnoid hemorrhage (SAH) from aneurysm rupture and delineate the clinical course of patients who suffer such a hemorrhage. The use of oral contraceptives, tobacco and alcohol are the factors of greatest interest. Other patient attributes considered will include age, gender, exercise, history of hypertension, and the use of stimulant drugs. The long-term goal is to reduce the incidence of this devastating disease by controlling its risk factors and by understanding better its pathophysiology. Risk factors will be evaluated using a population-based case- control study. All residents of Seattle, Washington, who have a SAH over a two year period will be identified and followed for at least one year. Based on the reported incidence of 10 to 28 cases per 100,000 persons per year and Seattle's population of around 500,000 persons, 100 to 280 cases of SAH would be expected to occur in Seattle over two years. For each case, two controls will be identified using random-digit telephone dialing and will be matched for age, gender, race and marital status. Because so many of the cases will die or be unable to supply reliable information, evaluation of risk factors will require the use of a surrogate, the case's spouse or significant other. Information about exposure to the risk factors of interest will be obtained by personal interview with the case surrogate and, when possible, the case. The same structured interview will be obtained from the two matched controls and their surrogates. Although in many instances the case will not be interviewed because of death or severe neurologic deficits, in all instances the case surrogate, the two matched controls and their surrogates will be interviewed. Estimates of the relative risk will be derived using both univariate and multivariable analyses. Primary analysis will involve comparison of responses from case surrogate and control surrogates. Reliability will be assessed by comparing the responses of controls to their surrogates and, when available, the cases and case surrogates. Descriptive information on the usual clinical course of SAH will come from the one-year to three-year follow-up of these patients, based on review of existing medical records.